RIVERSIDE, Calif. – A woman was shot to death after her boyfriend confronted two burglars who were apparently trying to break into a vehicle near their Southern California apartment early Thursday morning, police said.

Around 3:45 a.m., the man awoke to the sounds of a truck being broken into across the street from the victims' residence in Riverside, according to Riverside Police Department Officer Ryan Railsback.

He yelled out the window in an apparent effort to spook the burglars, who got into a white compact sedan and sped off, according to Railsback.

Moments later, gunfire erupted from outside the couple's building.

The suspects "appeared to be leaving, but then just a real short time later, drove by and fired the one shot," Railsback told KTLA, adding he was unsure what prompted them to return to the residence and open fire.

The woman was struck in the back by the gunfire, the officer said. Paramedics transported her to a local hospital where she was later pronounce dead.

Police have not identified the victim, saying only that she was about 40 to 50 years old.

The man and woman lived together and were believed to be boyfriend and girlfriend, according to Railsback.

At least two to three vehicle break-ins were reported in the immediate area to police after they responded to the shooting, Railsback said.

A description of the burglars or their vehicle was not immediately released. The shooter was only described as being a man.